The present invention relates to a novel thin-layer chromatographic plate.
The technique known as chromatography permits the separation of chemicals to a high degree of resolution. In general, chromatographic separations depend on the solubility, adsorption, or volatility of the molecules desirous of isolation. In general, every chromatographic system consists of two phases, a moving phase and a stationary phase. The moving phase necessarily flows past the stationary phase to effect the separation.
Thin-layer chromatography is classified under the general category of adsorption chromatography. In other words, the moving phase is a liquid and the stationary phase is a solid functioning as an adsorbing surface. Formation of the adsorbing surface takes place by the deposition of adsorbent on a flat supporting surface. Prior thin-layer chromatography plates normally consist of a piece of glass having a deposit of adsorbent material, such as silica gel, alumina, kieselguhr, cellulose, and the like, in a thin layer on one side thereof. Generally, the thin-layer deposit is 0.1 to 2.0 millimeters thick. A binding agent such starch or plaster of Paris holds the adsorbent material in place. The mixture to be separated is dissolved in any suitable solvent and applied as a spot to the adsorbent surface of the plate. The solvent evaporates in a stream of warm air. The plate having the spot thereupon is then placed vertically in a chamber in contact with the solvent. The solvent ascends the adsorbent layer by capillary action to a height of about 10 to 15 centimeters above the spot. The original spot is referred to as the "origin". The top layer of solvent as it flows up the plate is known as the "solvent front". A properly selected solvent will resolve the original spot of mixture into a series of spots corresponding to a component or several components. Spots may be visualized by spraying them with suitable color producing agents such as sulphuric acid, phosphorous, and the like.
Comparison of the pattern of spots, or chromatogram, to known chromatograms completes the identification process.
The migration distance of the constituent forming the spot compared to the movement of the solvent front is critical in many identifications. Currently, spotting guides are employed such as the SJ-1010 spotting guide, distributed by Analtech, Inc., Newark, Delaware. Such guides assist in the placement of the spot and measure the migration distance of the solvent front and component spots. However, imposition of a templet or guide is awkward and often injures the relatively fragile thin-layer plate. Also, analysis samples migrate with the moving solvent leaving no trace of the origin position. Another problem arises in that thin-layer plates are often intermixed and are later unidentifiable.
No known prior thin-layer plates possess permanent indicia visible on or in the vicinity of the surface of the layer of adsorbent material.